Electrical Energy Systems

Transcription

1 Electrical Energy Systems Course Code: ENG 368 Prof. Dr. Magdi M. El-Saadawi saadawi1@gmail.com 2/25/2017 Prof. Dr. Magdi El-Saadawi 1

2 Contents Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Electrical Power Systems: an Overview Electrical Power Generation Systems Electrical Power Transmission System Electrical Illumination Electrical Transformers Alternating Current Circuits 2/25/2017 Prof. Dr. Magdi El-Saadawi 2

3 Chapter 2 Electrical Power Generation Systems 2/25/2017 Prof. Dr. Magdi El-Saadawi 3

4 Chapter 2 Electrical Power Generation Systems 2.1 Generating Stations 2.2 Steam Power Stations (Thermal Station) 2.3 Nuclear Power Stations 2.4 Gas Turbine Power Plants 2.5 Hydro-electric Power Stations 2.6 Renewable Energy Systems Wind Power Photovoltaic Power System 2/25/2017 Prof. Dr. Magdi El-Saadawi 4

5 2.1 Generating Stations Electrical energy must be produced and transmitted to the point of use at the instant it is needed. The entire process takes only a fraction of a second. Energy is available in various forms from different natural sources such as pressure head of water, chemical energy of fuels, nuclear energy of radioactive substances etc. All these forms of energy can be converted into electrical energy by the use of suitable arrangements. 2/25/2017 Prof. Dr. Magdi El-Saadawi 5

6 The prime mover is driven by the energy obtained from various sources such as burning of fuel, pressure of water, force of wind etc. 2/25/2017 Prof. Dr. Magdi El-Saadawi 6

7 2.1 Generating Stations For example, chemical energy of a fuel (e.g., coal or solar) can be used to produce steam at high temperature and pressure. The steam is fed to a prime mover which may be a steam engine or a steam turbine. The turbine converts heat energy of steam into mechanical energy which is further converted into electrical energy by the alternator. Similarly, other forms of energy can be converted into electrical energy by employing suitable machinery and equipment. 2/25/2017 Prof. Dr. Magdi El-Saadawi 7

8 محطات التوليد 2.1 Generating Stations Bulk electric power is produced by special plants known as generating stations or power plants. The generating stations are classified as: (i) Steam power stations (ii) Hydroelectric power stations (iii) Gas turbine power stations (iv) Nuclear power stations (vi) Renewable energy plants 2/25/2017 Prof. Dr. Magdi El-Saadawi 8

9 2.2 Steam Power Stations (Thermal Stations) تعريف المحطات البخارية It is a generating station which converts heat energy of any fuel (coal, oil, or natural gas) into electrical energy 2/25/2017 Prof. Dr. Magdi El-Saadawi 9

10 2.2 Steam Power Stations (Thermal Stations) نظرية عمل المحطات البخارية Steam is produced in the boiler by utilizing the heat of the fuel. The steam is then expanded in the prime mover (i.e., steam turbine) and The steam turbine drives the generator which converts mechanical energy of the turbine into electricity. The steam is condensed in a condenser to be fed into the boiler again and the cycle is continued. 2/25/2017 Prof. Dr. Magdi El-Saadawi 10

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12 Disadvantages عيوب المحطات البخارية It pollutes the atmosphere due to the production of large amount of smoke and fumes. It must be installed near to a water source. It has a Low efficiency. 2/25/2017 Prof. Dr. Magdi El-Saadawi 12

13 مميزات المحطات البخارية Advantages Less initial cost as compared to other stations. It can be installed at any place irrespective of the existence of fuel, since the fuel can be easily transported Cost of generation and maintenance are lesser than that of other plants. It requires less space as compared to the hydroelectric power station. It can be used for water desalination in some countries. 2/25/2017 Prof. Dr. Magdi El-Saadawi 13

14 2.2.1 Equipment of Steam Power Station The main components of a steam power station explained in Fig. 2.2 are: 1. Boiler 2. Furnace 3. Steam turbine 4. Condenser 5.Alternator 6. Chimney 7. Auxiliaries 2/25/2017 Prof. Dr. Magdi El-Saadawi 14

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16 1. Steam generating equipment It composed of (i) Boiler and (ii) Boiler furnace (i) Boiler A boiler is a closed vessel in which water is converted into steam by utilizing the heat of fuel combustion. It is classified into the following two types: (a) Water tube boilers (b) Fire tube boilers 2/25/2017 Prof. Dr. Magdi El-Saadawi 16

17 Water tube boiler: water flows through the tubes and the hot gases of combustion flow over these tubes as explained by 2/25/2017 Prof. Dr. Magdi El-Saadawi 17

18 Fire tube boiler the hot products of combustion pass through the tubes surrounded by water as explained by Fig /25/2017 Prof. Dr. Magdi El-Saadawi 18

19 Comparison Water tube boilers have a number of advantages over fire tube boilers: It require less space, smaller size of tubes and drum, high working pressure due to small drum, less liable to explosion etc. Therefore, the use of water tube boilers has become universal in large capacity steam power stations. 2/25/2017 Prof. Dr. Magdi El-Saadawi 19

20 Comparison Water tube boilers have a number of advantages over fire tube boilers: It require less space, smaller size of tubes and drum, high working pressure due to small drum, less liable to explosion etc. Therefore, the use of water tube boilers has become universal in large capacity steam power stations. 2/25/2017 Prof. Dr. Magdi El-Saadawi 20

21 (ii) Boiler furnace. A boiler furnace is a chamber in which fuel is burnt غرفة لحرق الوقود وتحرير الطاقة به to liberate the heat energy The boiler furnace walls are made of a material that resist change of shape, weight or physical properties at high temperatures. refractory materials such as fire clay حرارى,طين silica etc. The shape and type of the furnace differ according to the type of fuel used. 2/25/2017 Prof. Dr. Magdi El-Saadawi 21

22 2. Steam turbine The heat energy of steam when passing over the blades of turbine is converted into mechanical energy. In a steam turbine the steam expands in the fixed blades, in doing so, the steam attains a high velocity and impinges against the moving blades. This results in impulsive force on the moving blades which sets the rotor rotating (see Fig. 2.5.) 2/25/2017 Prof. Dr. Magdi El-Saadawi 22

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27 4. Alternator (Generator) The alternator is coupled to a steam turbine and converts mechanical energy of the turbine into electrical energy. The alternator may be hydrogen or air cooled. The necessary excitation تغذية المجال المغناطيسى is provided by means of main and pilot exciters directly coupled to the alternator shaft as shown in Fig /25/2017 Prof. Dr. Magdi El-Saadawi 27

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29 3. Condensers A device which condenses the steam at the exhaust of turbine. It serves two important functions. Firstly, it helps in converting heat energy of steam into mechanical energy in the prime mover. Secondly, the condensed steam can be used as feed water to the boiler. There are two types of condensers, namely: Jet condenser and Surface condenser. 2/25/2017 Prof. Dr. Magdi El-Saadawi 29

30 3. Condensers The surface condenser shown in Fig. 2.6 is the mostly used one. It consists of a bank of horizontal tubes enclosed in a cast iron shell. The cooling water flows through the tubes and exhausted steam over the surface of the tubes. The steam gives up its heat to water and is itself condensed. فى بعض الدول تقام هذه المحطات بالقرب من البحر وفى هذه الحالة فإن بخار الماء الذى يتم تكثيفه ال يعود إلى الغاليات ولكن يتم تجميعه داخل خزانات لالستفادة به كماء عذب )تحلية مياه البحر( وهو ما يحدث حاليا فى بعض دول الخليج. 2/25/2017 Prof. Dr. Magdi El-Saadawi 30

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32 5. Chimney تهوية A chimney is a structure to provide ventilation for hot flue gases or smoke from a boiler, furnace to the outside atmosphere. Chimneys are typically vertical, to ensure that the gases flow smoothly outside The height of a chimney influences its ability to transfer flue gases to the external environment via stack effect. لو زاد طولها بدرجة كبيرة تقل قدرتها على سحب الغازات والعوادم للخارج 2/25/2017 Prof. Dr. Magdi El-Saadawi 32

33 6. Auxiliaries The auxiliaries include many equipments and devices that help to complete the work in the power plants such as: Fuel preparation system, Generator cooling system, Pumps and circulating water system, Monitoring and alarm system, Protection and metering, and control devices. These systems are required to make it possible for the major equipment to perform its function with the highest efficiency. 2/25/2017 Prof. Dr. Magdi El-Saadawi 33

34 2.2.2 Efficiency of Steam Power Stations (i) Thermal efficiency η thermal : The thermal efficiency of a modern steam power station is about 30%. If 100 calories of heat is supplied by fuel combustion, then mechanical energy equivalent of 30 calories will be available at the turbine shaft and rest is lost. 2/25/2017 Prof. Dr. Magdi El-Saadawi 34

35 2.2.2 Efficiency of Steam Power Stations (i) Overall efficiency η Overall : The overall efficiency of a steam power station is about 29%. It may be seen that overall efficiency is less than the thermal efficiency. This is expected since some losses (about 1%) occur in the alternator. 2/25/2017 Prof. Dr. Magdi El-Saadawi 35

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